Good question. Bishops are answerable each and every one personally to the Pope, who is the “president.” So I don’t know much about it all, but I don’t see how the USCCB could be an actual official organ of the Church’s hierarchy. It could almost be seen as a secular organization of US Bishops who come together to discuss issues and they elect a president to preside over the internal and external interactions of the organization, but that as an institution, it has no authority, and no Bishop has any authority other than what is granted him by the Pope.
I think that is right, but someone here can correct me and give a clearer picture of it all. It does seem kinda scary, like the potential for it to become a US “Bishop’s Union” or a US Bishop’s bloc. But if it is to help the US Bishop’s address the issues facing their respective dioceses, and come up with solutions to tough problems, and always remaining faithful to Scripture, Tradition and the authority of the Pope, than I think it is a good thing.